The present invention relates to an anti-locking hydraulic brake system of the type comprising a master brake cylinder and wheel brakes in communication therewith. A pump including a damping chamber, a check valve and a throttle delivers pressure to the brake circuit. The check valve is integrated into the damping device.
A system of this type is described, for example, in German patent document DE-OS 31 37 287. During actuation of the brake of this system, pressure fluid is forced from the master brake cylinder into the wheel brake such that the brake pads come into abutment with the brake shoes and with the brake disc, respectively, thereby causing a brake effect to be generated. Once the brake force rises beyond a predetermined level, the wheel may tend to lock. Upon occurrence of that condition, the brake conduit is blocked and pressure fluid is discharged from the wheel brake. By means of a pump, the pressure fluid is fed back into the master brake cylinder. As soon as the wheel becomes adequately reaccelerated, the brake conduit is re-opened to resupply pressure to the wheel brake for building up brake pressure.
To attain the described switch conditions, modulation valves are provided in the brake conduit and in the relief conduit. During blocking and opening of the brake conduit and of the relief conduit, respectively, pressure waves created in the hydraulic system are unavoidable. Such waves generate physical sonic vibrations which reach a substantial intensity and cause an unpleasant sensation to the driver of the automotive vehicle. Moreover, the noises can be interpreted as errors in the brake system with the danger that the driver may be caused to take unforeseeable corrective measures. According to the noted German patent, it is, therefore, suggested that a damping means and a throttle restriction means be provided in the pressure conduit between the pump and the master brake cylinder, and the termination of the pressure conduit into the brake conduit, respectively. Such measures smooth the undesirable pressure waves, thereby virtually ensuring a reduction in the noise which otherwise would result.
However, the above described system involves a particularly notable disadvantage. As the damping and throttle restriction means are coupled to the brake conduits, they also will become active during a non-controlled deceleration process. During such a deceleration process, the pressure fluid forced from the master brake cylinder to the wheel brakes not only is received by the wheel brake cylinder but also is received by the damping means, with the result that the pedal travel is extended.
It is, therefore, an object of the present invention to provide an anti-locking hydraulic brake system which, during the control phase, operates at a low pressure pulsation and at a minimized noise level and, during a non-controlled deceleration, avoids any unnecessary extension of the pedal travel.
According to another object, the brake system is to provide an inexpensive and compact construction requiring minimal assembling efforts. This problem is solved by the characterizing features of the present invention as set forth below.